Are teh images allowed to overlap anything? Other content? Will there be anything "in the same line" as the image?
If nothing can overlap (and you need it to wrap around stuff), you're basically looking for a float:bottom. Impossible. Design a different way to get what you want :).
If there is "nothing in the same line as the image", then you can just wrap a div around everything (in the <td>, which I don't see why you are using tables in the first place...), give that <div> some bottom padding, equal to the image. Give it position:relative as well, and then set an <img> in the HTML with that image. Position absolute it at the bottom of the cell.